^ I honestly think the issue of him killing was EXPLAINED well enough. It's a film, not a radio show!
Superman was heartbroken but put this situation behind him. To address that again undermines his ability to cope with his actions. While I do want that to be addressed in the sequel, I don't want a brooding, guilt-ridden Supes. I want a Superman who's at terms with his actions but never wants to go down that path again. Optimally, Superman wouldn't have to kill in his first updated movie. But that doesn't change what happens next. The next film should be more lighthearted, slow-paced, and character driven. But MOS is the reboot I think Superman needed to allow him to GET to that point. I give 8/10.